88 POTASSIUM LACTATE
Caustic potash by baryta should contain only traces of chlorides (faint opales-
cence with silver nitrate) and should not give the reactions for sulphates,
nitrates, cai'bonates, etc. (vide supra). Its content in KOH should not be less
than 80%, the remainder being water, which is inevitable in the purest products.
In potassium hydroxide by alcohol traces of chlorides, sulphates, silica (separa-
tion of flocks in test 7) and alumina (few Hocks after some hours in test 8) are
allowable ; the water should not exceed '-!o%.
In potassium hydroxide by lime small proportions of the above impurities,
such as chlorides, sulphates, etc., are tolerated. Its total alkalinity should be
not less than 80% and its content, of carbonate not more than 5%.
Crude caustic potash contains marked amounts of chlorides, sulphides, car-
bonates, etc. ; its value depends essentially on the proportion of KOH, deter-
mined as in 12.
KT :-.-.: 166-12
White (or faintly yellow if very old) crystals, extremely soluble in
water. It may contain bromides, chlorides, iodates, eyunides and the other
impurities found in the bromide. The principal impurities are tested for
as follows :
1. Iodates, Carbonates. -The powdered substance is treated with
dilute sulphuric acid ; effervescence indicates carbonates, and yellow colora-
tion, iodates. To 5 c.c. of the I : 20 solution are added ;i few drops of
starch paste and 5......(> drops of dilute; larta.ru.: acid (r : 50) ; in presence of
iodates, the liquid turns 'blue.
2. Chlorides, Bromides.- -About o'5 gram is dissolved in ammonia,
treated with silver nitrate, shaken, filtered, and the filtrate acidified with
nitric acid : with chloride or bromide, a, precipitate forms.
3. Cyanides........The solution (i : 20), treated with a, crystal of ferrous
sulphate, a drop of ferric chloride, eight drops of sodium hydroxide solution
and, after gentle heating, acidified with hydrochloric acid, becomes blue
if cyanides are present.
4. Sulphates, Metals, Alkaline Earths. ,S'<r Potassium Bromide (i).
Pure potassium iodide for pharmaceutical purposes should contain, accord-
ing to the Italian Hiarmacopuua, neither iodates, carbonates, sulphates, heavy
metals, nor cyanides. Test 2 (above) should give at most a, faint white or
For use in dyeing, an acid laetate of potassium, KlI6('.,()., + H()(v;,();i,
is sold under the name Lactolin as a yellowish-brown, syrupy liquid, con-
taining about 50% by weight of the acid laetate. Luctolin A and Lttctnlin
B represent the corresponding acid laetatcs of sodium and ammonium.
The. impurities of these products are the same as in lactic acid and are
investigated in the same way (sec Lactic Acid).
The free acid is determined by titralion with N-alkali in presence of
phenolphthalcin and the total acid by oxidation with permanganate, accord-
ing to Ulzer and Seidel (nee Lactic Acid).ution with powdered lead carbonate ami